The present invention concerns a ribbon cartridge for an electronic typewriter, and more particularly means for winding the ribbon with suitable tensioning and without the ribbon being folded.
In an electronic typewriter, if the hammer mounted on a carrier movable along a platen strokes a spoke of a print wheel, the character formed on the spoke collides along with an inked ribbon with a paper on the platen, thereby printing the character thereon. The ribbon is received into a cartridge, and mounted on the cartridge holder of the carrier. As the carrier moves along the platen, a ratchet mechanism causes the ribbon to be wound in a given direction.
Conventionally, a ribbon cartridge includes a supplying spool for supplying the ribbon and a winding spool for winding the ribbon supplied from the supplying spool. The drawbacks of the conventional ribbon cartridge are as follows:
First, the ribbon wound around the winding spool is frequently folded so that the contact of the winding spool and winding gear is adversely affected, thereby resulting in improper supplying of the ribbon;
Second, the construction of the resilient pressing means for forcefully contacting the moving winding spool, as the volume of the ribbon wound increases, with a winding gear is complicated;
Third, it is impossible to adjust the resilient force of the tension spring for tensioning the ribbon released from the supplying spool in accordance with the material and the width of the ribbon; and
Fourth, the ribbon is plastically strained and becomes loosely elongated by the hammer stroking. If the elongated ribbon is loosely positioned in front of the hammer, the stroked portion of the ribbon can not pass the position of the hammer and therefore, the next character printed becomes dimmer.